This invention relates to aircraft gas turbine engines and, more particularly, to sealing devices for axial dovetail compressor blades of such engines.
Aircraft gas turbine engines include compressor and turbine sections, each including one or more stages having an annular array of stator vanes adjacent to a rotating disk having an array of rotor blades. For certain stages, a rotor blade includes a dovetail-shaped base or root which is received within an axially-extending dovetail slot formed between adjacent dovetail posts on the rim of the rotor disk. The connection between the root of the rotor blade and the axial slot in the disk posts prevents radial and tangential movement of each rotor blade relative to the rotor disk.
In order to prevent axial movement of the rotor blades, blade retainers are mounted adjacent to axial slots in the rotor disk. These blade retainers preferably are secured directly to the rotor disk to minimize the weight and space occupied by such retainers. However, such retainers should be easily removable to facilitate replacement of the rotor blades.
To maximize compressor performance, air leakage through the blade dovetail connections with the disk should be minimized. Air leakage at this connection occurs through spaces between the blade root dovetail and adjacent disk posts of each such connection.
Previous attempts to seal these gaps between the blade roots and disk posts included applying a flexible seal material either to the blade root or to the disk post prior to assembly. This method of sealing proved unsatisfactory in that it made attachment of the rotor blades to the rotor disk difficult. Additionally, the sealing material had to be flexible to effect a seal, but the temperature range over which the sealing material was useful and therefore effective proved to be limited. Consequently, the extreme temperatures produced within the compressor renders seals of flexible sealing material inadequate to prevent compressor leakage.
An alternate method of sealing rotor blades on blade disks includes installing sheet metal between a hook formed on the rotor blade platform and an annular groove located on the disk spacer arm. This method of sealing was also proven to be problematic in that the position of the seal during engine operation is not determinant and therefore good sealing is not guaranteed. Another problem with this type of seal is that during engine operation, the centrifugal load of the seal is carried by the blade which increases the blade load, and consequently causes excessive wear problems on the blades. Additional material had to be added to both the blade dovetail and rotor disk to carry the load created by this type of seal. Therefore, a need exists for an improved apparatus for sealing axial dovetail rotor blades that eliminates the problems associated with previous sealing mechanisms, is inexpensive to manufacture and relatively easy to install.